I overheard an interesting conversation last night in a restaurant (I admit I cannot verify what was said so it's definitely rumour only).The gist of it was that dams like this were built with side spill outlets controlled by valves. These are meant to be used to control the maximum water level, to prevent over-topping of the wall but unfortunately these valves could no longer be opened at this dam, because the mechanism has rusted solid over many years.

The damaged area is a spillway which is designed to remove excess water when overtopped - for some reason the concrete facing has failed. If you look at the length of the spillway it can release huge amounts of excess water. Something similar happened to the Oroville Dam in the US not so long ago. The amount of water a spillway takes is massive, any small defect in the spill ways would rapidly become a large one.

Somewhere I have a photo of Laggan Dam (adjacent to the A86 Spean Bridge - Kingussie road) in full spate, the amount of water being released is astonishing. The mist of spray it created could be seen from several miles away. Standing next to it was truly awesome.

What I am curious about is where the bags being lifted are coming from.

Shy,

Was it done by Vertical Reference Long Line techniques....doors off or with bubble window doors.....or was the Crewman in back leaning out and providing directions to the Pilot flying.

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What you overheard was absolute nonsense. The current pictures clearly show the weir at the top of the spillway. This controls the maximum level, no valves involved. Outlet valves will be at the bottom, possibly in a tunnel within the dam. These will be in regular use to control the flow from the reservoir, and will be maintained in good working order, certainly not allowed to "rust solid over many years".

A couple of photos from google:

https://cdn.newsapi.com.au/image/v1/...698fe2230efdd1
https://pbs.twimg.com/media/EBB0QohWkAAdDWI.jpg

Merely pointing out the following

As 350 would be quicker, cheaper and more accurate with a longline, reasons

1. Longline with single pilot more accurate so bags could be placed not dropped
2. The pick up could be much closer to the dam and hence shorter flight time
3. Pilot would be more used to a high number of cycles per hour along with the crew eg probably a bag every 1.5 minutes or so
4. Like flying on instruments lifting quickly and safely and accurately is a perishable skill
5. Takes seconds to hook a bag on to a longline hook
6. Most RAF pilots don't do it that regularly. I am just a novice at doing it as i have around 700 hours lifting. The military dont fly a huge amount of hours and not solely lifting, not their fault it is all to do with budgets.

It is really tools for the job.
I would agree that great training exercise, great PR for RAF and shows the public that we sorely need our military. but the question was is it cheaper and more efficient !

If you can't get the bags closer because the roads are closed then the distance is the same.

What level of accuracy do you think could improve on a couple of centimetres - which is what was stated on the TV?

USL flying is absolute bread and butter to SH crews.

How much would a 350 operator charge the Govt for the service?

Is one 350 with a single bag really 3 times more efficient than one Chinook with 3 bags under it?

Wondering who filled those bags, and where. And how they got to the PUP if they were filled elsewhere.

SASless, I think you already know the answer to that question.

Two points:

There is now a new page on the BBC news site showing a photo attributed to the Canal and River Trust which shows the face of the dam. The "weir" is annotated as "Auxiliary Spillway" and appears to have been added later. The main spillway is lower down, as I was led to understand.

If the main spillway was serviceable, why is the water being pumped out from above (difficult, very expensive and potentially dangerous), rather than being allowed to drain naturally from below through the valves (i.e. main spillway)?

https://www.bbc.co.uk/news/uk-englan...shire-49220650

Crab

What is the roads closed got to do with it ? If you are the emergency services then you open them !
Lets assume that the bags are a mile from the drop zone, I suspect and knowing the area one could get them way closer. Then the 350 will have a turn round time of around 2 mins per bag. So 400 bags is 800 minutes or 13.3 hours call it 15 to be on the safe side.

We would have 2 pilots so at a real push could do those bags in a day

AS 350 £15000
Positioning £ 4000
Crew x 2 days £ 1800
Jet a1 £ 1800
Contingecy 15% £ 3120
So £ 25720 is the bill my company would charge. I might be wrong on teh distance, but that would be the advantage of the 350 and a longline.
Did you notice the bag rolling down the hill on the news ?

Because if you have evacuated an area because of the risk to life from the dam bursting, you would look pretty silly sending a load of civilian lorries inside that area if the dam did give way - it's just a sensible precaution you are happy to ignore to try and support your point about using a 350.

As Chinook 240 has pointed out - will you manage 24-hour ops in poor weather?

Photos do show the original masonry spillway running across the bottom of the dam. This won't be "lower down," it will also have a weir at the maximum water level. A spillway is an overflow, it can't be used to lower the water level. The outlet pipes will have a limited capacity - hence the pumping.

The map in post #23 shows the pick up point is a couple of miles outside the evacuated area, and at a higher elevation. The photos I added show a road across open moorland, no trees, no street lights, no utility poles - looks like as good a place as any.

Crab

So what is the cost of a chinnok then, i have told you how much I would do the job for, so money where your mouth is, how much is your chinook going to cost with all the crap that goes with it ?
Bet you the RAF can't even get close.to my cost. I am afraid the military is no where near as efficient as you think . Just because you can lift a 105 or an ISO container doesn't put you up there as utility Gods I am afraid

At the risk of boring. The cost of the Chinook and crew is unknowable. If they were not doing this repair, they would be doing normal exercise and training. You cannot easily calculate the cost per hour of items that are budgeted per year and NEVER intended to be sold by the hour. That's not what the Army do. When they are called in to lay sandbags and rescue people - is that charged? Do the local govt work out which commercial company could do that and how much first?

The cost of a commercial outfit is known, because that is what they do and are set up to charge by the hour/day or whatever. But, it is my contention, the Govt is going to tell the MoD to NOT charge the cost to anyone. So you cannot work out the cost.

Lastly, I think that many tax payers would rather the Army do this than a commercial outfit.